RF circuit module

ABSTRACT

A module for radio frequency signal circuits includes an electrically conductive housing. Coax connectors are secured to the rear face of the housing. A circuit board is contained within the interior spaced between sidewalls of the housing. A ground side of the circuit board includes a layer of electrically conductive material which is electrically connected to the housing. Coax cables extend within the interior of the housing from the coax connectors and between the ground side of the circuit board and an opposing sidewall. An opposite side of the circuit board contains circuit components interconnected with one another through a plurality of circuit paths.

I. BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention pertains to circuits for broad-band RF systems. Moreparticularly, this invention pertains to modular RF (radio frequency)circuit components.

2. Description of the Prior Art

In the telecommunications industry and more particularly in the videotransmission industry, broad-band radio frequency (RF) signals (i.e., 5MHz to 1 GHz) are carried over coax conductors from a headend toconsumers. At the headend of the system, numerous signals aremanipulated to achieve a wide variety of functions and objectives. Forexample, signals carried on numerous coax cables may be combined onto asingle coax conductor. Similarly, a signal on a main coax conductor maybe divided into a plurality of signals carried on branch coaxconductors. Additionally, signals may be added or removed from a mainconductor through directional couplers or the like.

In addition to combining, splitting, diverting or adding signals, theheadend will also include apparatus for modifying signals. For example,in order to adequately tune the system, it may be desirable to provideattenuators or the like to attenuate a signal to a desired level.Further, as a broadband RF signal is carried over a length of cable, thehigh frequency range of the signal may be attenuated more than a lowfrequency range of the signal. As a result, equalizers are utilized tomodify the signal to have a level intensity throughout its frequencyrange.

Throughout the system, performance characteristics are critical. Forexample, a common performance criteria is to maintain the flatness of asignal. Flatness refers to maintaining a level intensity of a signalthroughout its frequency range. For example, if the signal is attenuatedby 2 dB at 1 Ghz, then it is desirable that the signal be attenuated at2 dB at the 5 Mhz frequency. Further, the system needs to be tuned forimpedance matching.

Prior art headends include a wide variety of devices to accommodate andaccomplish the functions described above. It is desirable to provide anapparatus to accommodate the various functions required at the headendthrough a modular construction to permit ease of maintenance and cablemanagement in a headend. Such a device must accommodate the performancecharacteristics of the headend while permitting the modular constructionto enhance the cable management and organization of a headend.

II. SUMMARY OF THE INVENTION

According to a preferred embodiment of the present invention, a moduleis provided for containing a circuit for performing discrete functionson a radio frequency signal. The module comprises a housing ofelectrically conductive material. The housing has a front face and anopposite rear face. The front face and rear face are separated byopposite sidewalls and opposite end walls. A plurality of coaxconnectors are secured to the rear face with an outer shield of theconnectors electrically connected to the housing. A circuit board iscontained within the interior. The circuit board is generally parallelto and spaced between the sidewalls. The circuit board has a componentside and a ground side. The ground side includes a layer of electricallyconductive material which is electrically connected to the housing. Aplurality of coax cable connection locations are provided on the groundside of the circuit board. Each of the coax cable connections includes aground connection for connecting ground shields of coax cables to thelayer of electrically conductive material. The component side of thecircuit board includes a plurality of circuit components interconnectedwith one another and with the coax cable connection locations through aplurality of circuit paths. A plurality of coax cables are disposedwithin the interior and connected to individual ones of the coaxconnectors and the coax cable connection locations. Each of the coaxcables has a ground shield connected to the outer shields of theconnectors and to the ground connections of the coax cable connectionlocations. A plurality of cables are routed for the cables to bedisposed between the ground side of the circuit board and the opposingsidewall of the housing.

III. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a bottom end, front face and right sidewall perspective viewof one embodiment of a module according to the present invention shownin exploded view (with internal cables omitted);

FIG. 2 is a left side plan view of the module of FIG. 1;

FIG. 3 is a right side plan view of the module of FIG. 1;

FIG. 4 is a front elevation view of the module of FIG. 1;

FIG. 5 is a rear elevation view of the module of FIG. 1;

FIG. 6 is a bottom end view of the module of FIG. 1;

FIG. 7 is a top end view of the module of FIG. 1;

FIG. 8 is a rear, right side and top end exploded view of the module ofFIG. 1 with a cover removed;

FIG. 9 is a perspective view of internal components of the module ofFIG. 1;

FIG. 9A is a top plan view of a printed circuit board and attachedcomponents;

FIG. 10 is an opposite side plan view of the components of FIG. 9;

FIG. 11 is a side cross-sectional view of the module of FIG. 1;

FIG. 12 is a view similar to that of FIG. 1 showing in exploded formatan alternative embodiment of the present invention;

FIG. 13 is a right side plan view of the module of FIG. 12;

FIG. 14 is a left side plan view of the module of FIG. 12;

FIG. 15 is a front elevation view of the module of FIG. 12;

FIG. 16 is a rear elevation view of the module of FIG. 12;

FIG. 17 is a bottom end view of the module of FIG. 12;

FIG. 18 is a top end view of the module of FIG. 12;

FIG. 19 is a bottom end, front face and right sidewall perspective viewof a third embodiment of a module according to the present inventionshown in exploded view (with internal cables omitted);

FIG. 20 is a right side plan view of the module of FIG. 19;

FIG. 21 is a left side plan view of the module of FIG. 19;

FIG. 22 is a front elevation view of the module of FIG. 19;

FIG. 23 is a rear elevation view of the module of FIG. 19;

FIG. 24 is a bottom end view of the module of FIG. 19;

FIG. 25 is a top end view of the module of FIG. 19;

FIG. 26 is a perspective view of a first embodiment of a chassis forholding modules according to the present invention;

FIG. 27 is a perspective view of a second embodiment of a chassis forholding modules of the present invention; and

FIG. 28 is a perspective view of a third embodiment of a chassis forholding modules of the present invention.

IV. DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the several drawing figures in which identical elementsare numbered identically throughout, a description of the preferredembodiment of the present invention will now be provided.

With initial reference to FIGS. 1 through 11, a module 10 according tothe present invention will be described for use as a splitter/combinermodule for splitting a main signal into a plurality of branch signalsor, alternatively, combining a plurality of branch signals into a commonmain signal. The module 10 includes a housing having a front face 14, arear face 16. The front face and rear face 14, 16 are separated byopposing sidewalls 18, 20 and opposite end walls 22, 24. The housing 12is formed of electrically conductive material. Preferably, the materialis nickel-plated aluminum.

Sidewall 18 and end walls 22, 24 are integrally formed as a boxconfiguration with walls 22, 24 having inwardly protruding peripheralledge 26. Rear wall 16 is secured to walls 18, 22, 24 by screws 28. Thesidewall 20 is fastened to the ledge 26 by a plurality of screws 28received in aligned bolt holes 30 of sidewall 20 and threaded bolt holes32 on the peripheral ledge.

The sidewall 20 is sized to have a length greater than the longitudinaldimension between walls 22, 24 such that ends 20 a, 20 b extend beyondends 22, 24 as flanges for purposes that will be described.

The front cover 14 includes extending edges 14 a, 14 b which extendbeyond ends 22, 24. The front cover further has an internal ledge 34(shown in FIGS. 1, 8 and 11) on an interior surface of the cover 14. Theledge 34 is sized to extend into the interior of the housing when thefront cover 14 is attached to the housing.

The front cover 14 and sidewall 20 are secured to the housing by thescrews 28 received within aligned bolt holes. The screws 28 arepreferably positioned at one-half inch on-center spacings to prevent EMIleakage as is conventional.

The front cover 14 includes a plurality of openings 36 the function ofwhich will be described with the openings 36 arranged linearly along theface 14. Similarly, the front cover 14 includes an opening 38 sized topass a coax connector 41 for purposes that will become apparent.

A plurality of coax connectors 40-0 through 40-8 are secured to the rearface 16. Each of the coax connectors is identical. Such connectors areconventional and include a central conductor surrounded by a groundedshield. The grounded shields of the coax conductors are in directphysical and electrical contact with the electrically conductivematerial of the rear face 16.

Contained within the interior of the housing 12 is a printed circuitboard 44. The printed circuit board 44 is supported on posts 42 byscrews 43. The posts 42 are electrically conductive and connected towall 18. The printed circuit board 44 includes a component side 44 a anda ground side 44 b (see FIG. 9). The ground side 44 b opposes the wall18 and the component side 44 a opposes wall 20. The printed circuitboard 44 is maintained in parallel, spaced relation between the walls18, 20 by supports 42.

A layer 44 c (FIG. 9) of electrically conductive material (such as asheet layer of copper) is provided on the exterior surface of surface 44b.

A plurality of coax cable connection locations 48-0 through 48-8 areprovided on the ground side 44 b of the printed circuit board 44. Eachof the coax cable connection locations 48-0 through 48-8 include aground connection for connecting the ground shields of a coax cable tothe conductive layer 44 c.

A plurality of circuit components are disposed on the component side 44a of the printed circuit board 44. In the embodiment shown, thecomponents include a solid state directional coupler 50 and three solidstate splitter/combiners 52-1, 52-2 and 52-3.

It will be appreciated that a solid state directional coupler 50 is acommercially available item, and an example of such is a 20 dB couplerProduct No. CPL/20BE-08A3 sold by TRAK Microwave, 4726 Eisenhower Blvd.,Tampa, Fla. 33634-6391. Similarly, solid state splitter/combiners 52-2through 52-3 are commercially available one-by-four splitters andexamples of such are Product No. SPL/4BE-53D sold by TRAK Microwave.Splitter/combiner 52-1 is a one-by-two splitter such as Product No.SPL/2BE-53D of TRAK Microwave.

The splitter/combiners each receive a signal and divide an RF signalinto two signals of equal strength. Splitter/combiners 52-2 and 52-1 areelectrically connected in series. Similarly, splitter 52-3 is connectedin series with splitter 52-1 such that splitter 52-3 is connected inparallel to splitter 52-2.

The electrical connection of the components 50 and 52-1 through 52-3 isprovided through a plurality of circuit paths 53 (FIG. 9A) contained onthe surface 44 a where the circuit paths connect the components 50, 52-1and 52-3 with the coax connection locations 48-0 through 48-8. Thecircuit paths connect the components and the connection locations suchthat connectors 40-0 is connected to the directional coupler 50 with aportion of the signal diverted from the directional coupler 50 to thecoax monitor connector 41 through cable 41-1. Preferably, coupler 50provides a −20 dB monitor signal.

The main signal from the directional coupler 50 is passed to thesplitter/combiner 52-1 which divides the main signal into two signalswith one passed along the circuit paths to splitter/combiner 52-2 andthe other passed to splitter/combiner 52-3. Each of splitters 52-2 and52-3 split a signal into four signals resulting in a total of eightbranch signals passed to connection locations 48-1 through 48-8.

In the preceding paragraph, a signal is described as coming into thedirectional coupler from connector 40-0 and then eventually split andpassed to connectors 40-1 through 40-8. With the directional coupler 50arranged in the schematic shown of FIG. 3, such a signal flow path wouldresult in losing a monitor function at monitor port 41. With thisschematic shown in FIG. 3, signals passed into connectors 40-1 through40-8 are attenuated and combined to a main signal which is then passedthrough directional coupler 50 to OUT port 40-0. A portion of the mainsignal is then passed from the directional coupler 50 to the monitorport 41 so that the signal may be monitored. If it is desirable to passa signal into connector 40-1 for division into branch signalsdistributed to connectors 40-1 through 40-8, a different directionalcoupler 50 can be provided such that a signal from connector 40-0 can bemonitored at port 41.

Before the branch signals are passed to the connection locations, theyare passed through attenuator components. Each of the attenuatorcomponents is identical and includes a base member 60-1 through 60-8which is secured to the component side 44 a of the printed circuit board44 along a leading edge 44 d of the printed circuit board and with thebase members 60-1 through 60-8 arranged in a linear array.

A plurality of the attenuator plugs 64-1 through 64-8 are provided to bereleasably connected to individual ones of the base member 60-1 through60-8. The attenuator plugs 64-1 through 64-8 provide an attenuation to asignal to each of the branch circuits being sent to connectors 40-1through connectors 40-8.

Attenuator plugs and base members are commercially available items suchas those sold as Product No. F-7520-A (for a 20 dB attenuator) throughCommunication Associates 1750 T-'Coleman Road, Anniston, Ala. 36207. Theplugs 64-1 - 64-8 can be individually selected to provide a discreteamount of attenuation to a signal. For example, a “zero” plug can beinserted into a base member to provide 0 dB attenuation. Alternatively,at an option of a technician, the 0 dB plug may be replaced with a 15 dBplug to provide 15 dB attenuation to a signal. As a result, each of thebranch circuits can be individually provided with a unique attenuationselected at an option of a technician. The holes 36 on the front face 14are arranged and sized such that each of the attenuator plugs extendsthrough individual ones of the holes 36 to be grasped by an operator. Asa result, an operator can remove and replace an attenuator plug withoutneeding access to the interior of the housing 12.

To provide EMI leakage protection, the front face 14 is provided with aremovable cover 100 surrounding the array of holes 36. A deformable,conductive seal 102 (silicon gasket impregnated with silver particles)is provided between the cover 100 and face 14. Threaded connections 104on the cover 100 are aligned with threaded holes on the standoff posts106 such that the cover 100 can be secured to the face 14 by turning thethreaded connectors 104 into the standoff posts 106. As the threadedconnection 104 is tightened, the edge of the cover 100 compresses intothe seal 102 to thereby compress the seal 102 against the face 14 toprovide an effective EMI seal.

The device thus described performs splitter/combiner functions withconnector 40-0 being a main connector and with connectors 40-1 through40-8 being branch connectors. In other words, a signal admitted toconnector 40-0 is split into eight equal signals passed to connectors40-1 through 40-8. Further, the main signal may be monitored throughforward connector 41.

As shown in the drawings, all of the connectors 40-0 - 40-8 areconnected to the connection locations 48-0-48-8 via coaxial cables 70-0through 70-8 such that the ground shield of the coaxial cable iselectrically connected to the ground shield of the connectors 40-0through 40-8, respectively, as well as connected to the conductive layer44 c.

In RF circuits, impedance matching is critical. The parallel relation ofthe electrically conductive layer 44 c to the sidewall 18 of the housing12 presents a small capacitance. Further, the spaced relation of thecircuit paths 53 to the opposite sidewall 20 presents a minutecapacitance. Capacitance between the housing and the circuit componentsare referred to as “parasitic reactants”. Further, there is naturalcapacitance or reactance of components on the circuit board 44. Thepathways 53 are tuned to balance the capacitance. The pathways 53 aretuned by adjusting the size of the circuit pathways 53 such that theypresent an inductance selected to balance the parasitic reactances andthe circuit board reactances. It will be appreciated that sizing circuitpathways to present a desired impedance is well known in the art. Also,the cables 70-0 through 70-8 are routed between the ground surface 44 cof the circuit board 44 and its opposing sidewall 18 of the housing 12.By routing the cables 70-8, 70-8 on this side of the circuit board 44and avoiding placing the cables adjacent any of the circuit componentsor circuit pathways, undesirable reactances are avoided.

With the structure thus described, the desired circuit function isattained in a modular format. Further, in addition to impedance matchingcircuit components, the selection and arrangement of components permitsa high performance module with impedance matching throughout and withdesired flatness of a signal across the broad band frequency range.

As shown in the drawings, the forward ledge 34 includes a plurality ofresilient spring contacts 35 mounted on the ledge 34-and positioned toswipe against the electrically conductive layer 44 c as the cover 14 isplaced on to the housing to insure enhanced electrical contact betweenthe conductive layer 44 c and the cover 14 so that all elements aregrounded when coaxial cables are connected to the rear connectors.

To further protect the signal, the front cover 100 is provided on frontend 14 to cover and enclosed all attenuator plugs 64-1-64-8 extendingthrough holes 36. The cover 100 prevents EMI interference which wouldotherwise occur by uncovered plugs 64 extending through holes 36.

The foregoing discussion with respect to FIGS. 1-11 described anembodiment of the present invention for an RF module having splitterfunctions and monitor functions. FIGS. 12-18 illustrate the invention ina different embodiment for an equalizer circuit. In an equalizercircuit, an equalizer component is used to provide the same degree ofattenuation at the extremes of the RF bandwidth. Elements similarlynumbered with respect to the previously described embodiment arenumbered similar in FIGS. 12-18 with the addition of an apostrophe todistinguish between the embodiments.

In FIG. 12, a module 10′ includes a housing having a base 18′ andsidewalls 22′, 24′. The module 10′ further includes a front face 14′ anda rear face 16′. A side cover 20′ closes the module 10′.

As in the previously described embodiment, the present inventionincorporates a printed circuit board 44′ containing circuit components.The circuit board 44′ is maintained in parallel spaced relation betweenthe sidewall 20′ and the lower sidewall 18′ by support posts 42′ andassociated screws 43′.

For the equalizer circuit, the circuit components include a directionalcoupler 50′ and an equalizer component 64′ removably secured to a basemember 60′. The equalizer 64′ may be removed or replaced through anopening 36′ in the forward wall 14′.

The rear wall 16′ contains coax connectors 40-0′, 40-1′ and 40-2′.Coaxial cables (not shown) extend from the coax connectors 40-0′ through40-2′ and beneath the printed circuit board 44′ in a manner identicalwith that previously described. Further, as in the previous embodiment,the circuit board 44′ contains an electrically conductive layer opposingand electrically connected to surface 18′. Also, the circuit paths onthe upper surface of the board 44′ are provided to balance impedances aspreviously described.

The coaxial cables will extend between the board 44′ and the surface 18′for reasons previously discussed. The circuit paths on the board 44′ aredisposed such that an incoming circuit from incoming signal from 40-0′is passed to the equalizer and then to the directional coupler 50′.Further, the separate incoming signal can be passed from connector 40-1′to directional coupler 50′ encoupled with the signal from the equalizer64′ with the coupled signal passed to the output connector 40-2′. Asupport 51′ is mounted within the interior of the housing to guideequalizer 64′ toward base member 60′ in required alignment. As with theprevious embodiment, a cover 100′ covers the front face 14′ togetherwith a gasket 102′ to prevent EMI.

All other features of the module 10′ are similar to the module 10including the external dimensions and tabs of the module such that amodule 10′ may be interchangeable in a chassis with a module 10.Further, the module 10′ has the same impedance matching and parasiticreactance compensation previously mentioned with respect to module 10.As a result, the invention of module 10 is incorporated into module 10′with module 10′ showing a specific embodiment of the invention for usewith an equalizer component. It will be appreciated that equalizercomponents 64′ are commercially available items. An example of such isproduct number G75-000 of ADC Broadband Communications Division, 999Research Parkway, Meridan, Conn. 06450.

FIGS. 19-25 illustrate a third embodiment of the present invention foruse in a 6-port directional coupler. The directional couplers are usedto split or add multiple signals. Elements similarly numbered withrespect to the previously described embodiments are numbered similarlyin FIGS. 19-25 with the addition of a double apostrophe to distinguishbetween the embodiments.

In FIGS. 19-25, a module 10″ includes a housing 12″ having a base 18″and sidewalls 22″, 24″. The module 10″ further includes a front face 14″and a rear face 16″. A side cover 20″ closes the module 10″.

As in the previously described embodiments, the present inventionincorporates a printed circuit board 44″ containing circuit components.The printed circuit board 44″ is maintained in parallel spaced relationbetween the sidewalls 20″ and the lower sidewall 18″ by support post 42″and associated screws 43″.

The circuit components include six directional couplers 50-1″ through50-6″, each with individually associated attenuator plugs 64-1″ through64-6″ which are removably secured to individual base members 60-1″through 60-6″. Each of the attenuator plugs 64-1″ through 64-6″ may beremoved or replaced through openings 36″ in the forward wall 14″.

The rear wall 16″ contains coax connectors 40-0″ through 40-6″. Coaxialcables (not shown in FIGS.) extend from each of the coax connectors40-0″ through 40-6″ and beneath the printed circuit board 44″ in amanner identical with that described with reference to the firstpreferred embodiment of FIG. 1. Further, as in the previous embodiment,circuit board 44″ contains an electrically conductive layer opposing andelectrically connected to surface 18″. Also, the circuit paths on theupper surface of the board 44″ are provided to balance impedances aspreviously described.

The coaxial cables will extend between the board 44″ and the surface 18″for reasons previously discussed. The circuit paths on the board 44″ aredisposed such that six incoming signals may be separately connected toeach of connectors 40-1″ through 40-6″ and passed through the individualattenuators 64-1″ through 64-6″ into the directional couplers 50-1″through 50-6″ where the six signals will be joined into a common outputsignal passed to connector 40-0″. As with the previous embodiment, acover 100″ covers the front face 14″ together with a gasket 102″ toprevent EMI.

All of the features of the module 10″ are similar to the modules 10, 10′including the external dimensions and tabs of the modules such that themodules 10″, 10′ and 10 may be interchangeable in a common chassis.Further, the module 10″ has the same impedance matching and parasiticreactants compensation previously mentioned with respect to module 10.As a result, the invention of modules 10 and 10′ is incorporated intomodule 10″ with module 10″ showing a specific embodiment of theinvention for use with a 6-port directional coupler circuit.

FIG. 26 shows a first chassis 200 for housing a plurality of modules 10.The chassis 200 includes horizontally spaced apart sidewalls 202, 204and vertically spaced apart top and bottom walls 206, 208. The top andbottom walls 206,208 are spaced apart by a distance substantially equalto a distance between the end walls 22, 24 of the module 10.

Each of the top and bottom walls 206, 208 includes a plurality ofvertically aligned grooves 210. The grooves 210 are sized to slidablyreceive the projecting flanges 20 a, 20 b of the module 10 such that amodule may be slidably inserted into the frame 200 with the modules 10vertically positioned. In the embodiment shown, there are 12 pairs ofvertically aligned grooves 210 such that 12 modules may be inserted intothe frame 200. Since the flanges 20 a, 20 b of the modules 10 are offsetfrom a longitudinal plane of the module 10, the grooves 210 are offsetfrom module receiving spaces so that the entire open space between thesidewalls of the frame may be filled with modules. Also, the grooves 210are spaced apart a distance selected such that as modules are slidablyinserted into the frame, adjacent modules are positioned with a smallspacing between opposing sidewalls of adjacent modules 10.

Locking screws 214 are provided on the projecting tabs 14 a, 14 b of thefront walls 14 of the modules 10. Corresponding threaded locking holes216 are provided on both the top and bottom walls 206, 208 of the frame200. The screws 214 are not centrally positioned on the tabs 14 a, 14 b.Instead, they are laterally offset from a central longitudinal axis ofthe front wall 14. The holes 216 are similarly offset to require that amodule 10 be placed in the frame 200 in a desired orientation and cannotbe flipped 180° to be inserted in an undesired orientation. The frame200 also includes a hinged cover 218 which preferably is transparent topermit an operator to inspect the interior. Cable management brackets220 are provided on the rear of the chassis 200.

From time to time, a customer or purchaser of the modules 10 may desireto hold the modules 10 in a horizontal alignment rather than thevertical alignment of FIG. 26. An alternative chassis 200′ is shown inFIG. 27 for holding the modules 10 in a horizontal alignment. In FIG.27, the chassis 200′ includes horizontally spaced apart sidewalls 202′,204′ and vertically spaced apart top and bottom walls 206′, 208′. Anintermediate wall 209′ is provided midway and parallel to side walls202′, 204′. The distance between either of side walls 202′, 204′ andmidwall 209′ is equal to a distance between the end walls 22, 24 of themodule 10.

Each of the sidewalls 202′, 204′ and the midwall 209′ include aplurality of horizontally aligned grooves 210′. The grooves 210′ aresized to slidably receive the projecting flanges 20 a, 20 b of themodule 10 such that a module may be slidably inserted into the frame200′ with the module 10 horizontally positioned.

In the embodiment shown in FIG. 27, there are six pairs of horizontallyaligned grooves 210′ on both sides of the center wall 209′ such that theframe 200′ can contain a total of 12 modules. As a result, chassis 200and 200′ give an operator the opportunity to contain the exact samenumber of modules 10 in either a horizontal or a vertical alignment asthe operator may select.

Also, the locking screws 214 of the modules are aligned with lockingholes 216′ on the side walls 202′, 204′ and mid wall 209′. Since thescrew 214 are not centrally positioned on tabs 14 a, 14 b, and the holes216′ are not centrally positioned in modules receiving spaces, a module10 must be placed in the frame 200 in a desired orientation and cannotbe flipped 180° to an undesired orientation. As in the embodiment ofFIG. 26, the frame 200′ of FIG. 27 includes a hinged cover 218′ andcable management brackets 220′.

Finally, FIG. 28 shows a chassis 200″ which may be used in the eventthat an operator does not wish to have a combined total of 12 modulesbut instead only wishes to have a fewer number of modules. Chassis 200′retains two modules 10 in side-by-side horizontal alignment and includesmounting brackets 201 for mounting to a frame structure so that anoperator can elect to mount pairs of modules at a time rather thantwelve modules 10. Frame 200″ is similar to frame 200′ in that it has anintermediate wall 209″ between side walls 202″ and 204″ with the lockingscrews 214 received within holes (not shown) of walls 202″, 204″ and209″.

1. A module for containing a circuit for performing discrete circuitfunctions on a radio frequency signal, said module comprising: a housingof electrically conductive material defining an enclosed interior; saidhousing having a front face and an opposite rear face separated byopposite sidewalls and opposite end walls; a plurality of coaxconnectors secured to said rear face with an outer shield of saidconnectors electrically coupled to said housing; a circuit boardcontained within said interior and positioned generally parallel to andspaced between said sidewalls; said circuit board having a componentside opposing a first of said sidewalls and a ground side opposing asecond of said sidewalls; said ground side including a layer ofelectrically conductive material electrically connected to said housing;a plurality of coax cable connection locations on said ground side ofsaid circuit board, each of said coax cable connections including aground connection for connecting ground shields of coax cables to saidlayer of electrically conductive material; said component side of saidcircuit board including a plurality of circuit components interconnectedwith one another and with said coax cable connection locations through aplurality of circuit paths; a plurality of coax cables disposed withinsaid interior and connected to individual ones of said coax connectorsand said coax cable connection locations, each of said coax cableshaving ground shields connected to said outer shields of said connectorsand to said ground connections of said coax cable connection locations;and said plurality of cables routed for said cables to be disposedbetween said ground side of said circuit board and said second of saidsidewalls.
 2. A module according to claim 1 wherein said circuit pathsare sized to have an impedance selected to balance a parasitic reactancebetween said circuit board and said housing.
 3. A module according toclaim 1 wherein said plurality of components includes splittercomponents for receiving a main signal from one of said coax connectionlocations and dividing said main signal into a plurality of branchsignals delivered along said circuit paths to individual remaining onesof said coax connection locations.
 4. A module according to claim 1wherein said splitters components are adapted to act as combinercomponents for receiving said plurality of branch signals from saidindividual ones of said coax connection locations and combining saidbranch signals into said main signal delivered along one of said circuitpaths to said one of said coax connection locations.
 5. A moduleaccording to claim 3 wherein said splitter components includes at leasta first splitter and a second splitter connected in series.
 6. A moduleaccording to claim 5 wherein said splitter components includes a thirdsplitter connected in series with said first splitter and in parallelwith said second splitter.
 7. A module according to claim 3 wherein saidcircuit components include a plurality of attenuators associated withindividual ones of said branch circuits.
 8. A module according to claim7 wherein said attenuators include a variable attenuator component forvarying an amount of attenuation of said attenuators.
 9. A moduleaccording to claim 8 wherein said attenuators includes a firstattenuator component mounted on said component side of said circuitboard and said variable attenuator component removably secured to saidfirst component with said variable attenuator component selected for afixed desired attenuation.
 10. A module according to claim 9 wherein:said attenuators are positioned adjacent said front face; said frontface having an opening sized to pass said second variable attenuatorcomponent through said front face; an electrically conductive coverreleasably secured to said front face and sized to cover said opening.11. A module according to claim 10 wherein said cover and said frontface include an electrically conductive, mechanically deformable seal.12. A module according to claim 1 wherein said front face is removablefrom a remainder of said housing and includes electrically conductive,mechanically resilient conductors extending between said front face andsaid layer of conductive material.
 13. A module according to claim 12wherein said front face includes a protruding ledge disposed to supporta leading edge of said circuit card.
 14. A module according to claim 3wherein said circuit components include a directional coupler fordiverting a portion of said main signal to a connector locationconnected to a monitor coax connector.
 15. A module according to claim14 wherein said monitor coax connector is exposed on said front face.16. A module according to claim 1 wherein said circuit componentsinclude a directional coupler.
 17. A module according to claim 16wherein said components include an equalizer for equalizing a radiofrequency signal along a frequency range.
 18. A module according toclaim 17 wherein said equalizer includes a first equalizer componentmounted on said component side of said circuit board and a variableequalizer component removably secured to said first component with saidvariable equalizer component selected for a fixed desired radiofrequency equalization.
 19. A module according to claim 18 wherein: saidequalizer is positioned adjacent said front face; said front face havingan opening sized to pass said second variable equalizer componentthrough said front face; an electrically conductive cover releasablysecured to said front face and sized to cover said opening.
 20. Achassis and module combination for permitting selective housing of aplurality of modules containing radio frequency circuits, saidcombination comprising: A. a plurality of modules each having: a housingof electrically conductive material defining an enclosed interior; saidhousing having a front face and an opposite rear face separated byopposite sidewalls and opposite end walls, with each of said faces andsidewalls being of predetermined dimension and with said sidewalls beingparallel to one another; a plurality of coax connectors secured to saidrear face with an outer shield of said connectors electrically coupledto said housing; a circuit board contained within said interior andpositioned generally parallel to and spaced between said sidewalls; saidcircuit board having a component side opposing a first of said sidewallsand a ground side opposing a second of said sidewalls; said ground sideincluding a layer of electrically conductive material electricallyconnected to said housing; a plurality of coax cable connectionlocations on said circuit board, each of said coax cable connectionsincluding a ground connection for connecting ground shields of coaxcables to said layer of electrically conductive material; said componentside of said circuit board including a plurality of circuit componentsinterconnected with one another and with said coax cable connectionlocations through a plurality of circuit paths; said circuit componentsselected to perform a circuit function on a radio frequency signalsupplied to one of said connectors and to provide an output radiofrequency signal to a remainder of said connectors; a plurality of coaxcables disposed within said interior and connected to individual ones ofsaid coax connectors and said coax cable connection locations, each ofsaid coax cables having ground shields connected to said outer shieldsof said connectors and to said ground connections of said coax cableconnection locations; each of said end walls having a projecting flangeextending in a common plane generally parallel to said sidewalls andwith said common plane offset from a central longitudinal axis of saidhousing; said front face including end portions extending beyond each ofsaid end walls; a locking member secured to each of said end portionsand having a locking end extending through a rear surface of said endportions; at least one of said locking members positioned offset from alongitudinal axis of said front face; B. a first chassis having: a firstchassis frame including horizontally spaced apart first sidewalls andvertically spaced apart first top and bottom walls with said first topand bottom walls spaced apart by a distance substantially equal to adistance between said end walls of said modules; each of said first topand bottom walls including a plurality of vertically aligned firstgrooves sized to slidably receive said projecting flanges; said firstgrooves spaced along said first top and bottom walls for a predeterminednumber of said modules to be slidably received within said first framein a vertical orientation with said longitudinal axis of said front facevertically disposed and with opposing sidewalls of adjacent modulesnarrowly spaced apart; a plurality of first mating lock members on eachof said first top and bottom walls and positioned to mate with saidlocking members of said modules when said modules are received withinsaid first frame in a predetermined orientation and with said flangesreceived within said first grooves; C. a second chassis having: a secondchassis frame including horizontally spaced apart second sidewalls andvertically spaced apart second top and bottom walls; an intermediatewall extending vertically between said second top and bottom walls andcentrally positioned between said second sidewalls with saidintermediate wall dividing said second frame into a left column and aright column; said second sidewalls spaced from said intermediate wallby a distance substantially equal to a distance between said end wallsof said modules; each of said second sidewalls and intermediate wallincluding a plurality of horizontally aligned second grooves sized toslidably receive said projecting flanges; said second grooves spacedalong said second sidewalls and said intermediate wall for half of saidpredetermined number of said modules to be slidably received within saidleft column of said second frame in a horizontal orientation with saidlongitudinal axis of said front face horizontally disposed and withopposing sidewalls of adjacent modules narrowly spaced apart; saidsecond grooves further spaced along said second sidewalls and saidintermediate wall for half of said predetermined number of said modulesto be slidably received within said right column of said second frame ina horizontal orientation with said longitudinal axis of said front facehorizontally disposed and with opposing sidewalls of adjacent modulesnarrowly spaced apart; and a plurality of second mating lock members oneach of said second sidewalls and intermediate wall and positioned tomate with said locking members of said modules when said modules arereceived within said second frame in a predetermined orientation andwith said flanges received within said second grooves.